The Flow Cytometry Laboratory functions as a shared resource for cell analysis and sorting. The laboratory assists a wide range of investigator-directed research from clinically related studies of primary malignant cells and their normal counterparts, stem cells and gene therapy, to fundamental studies of developmental biology, gene regulation, and neoplastic transformation. The resource supports population based studies of genomic instability and changes in human solid tumors. Since its inception in 1978, the resource has continued to enhance its instrumentation, sophistication of usage and overall level of use. The laboratory continues to maintain its College of American Pathology accreditation for clinically related investigation. In addition to the maintenance and upgrade of resource equipment, the Flow Cytometry Laboratory actively assists investigators and their laboratories in experimental design, sample preparation, development of novel techniques, analysis and interpretation of data, and training in the operation of the instrumentation. This application requests continued support for a resource which continues to fulfill an essential role for peer reviewed research.